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# Working with Amazon S3 Bucket Policies
![\[JavaScript code example that applies to Node.js execution\]](http://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/images/nodeicon.png)
**This Node.js code example shows:**
+ How to retrieve the bucket policy of an Amazon S3 bucket.
+ How to add or update the bucket policy of an Amazon S3 bucket.
+ How to delete the bucket policy of an Amazon S3 bucket.
## The Scenario
In this example, a series of Node.js modules are used to retrieve, set, or delete a bucket policy on an Amazon S3 bucket. The Node.js modules use the SDK for JavaScript to configure policy for a selected Amazon S3 bucket using these methods of the Amazon S3 client class:
+ [https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#getBucketPolicy-property](https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#getBucketPolicy-property)
+ [https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#putBucketPolicy-property](https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#putBucketPolicy-property)
+ [https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#deleteBucketPolicy-property](https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#deleteBucketPolicy-property)
For more information about bucket policies for Amazon S3 buckets, see [ Using Bucket Policies and User Policies](https://docs.aws.amazon.com/AmazonS3/latest/userguide/using-iam-policies.html) in the *Amazon Simple Storage Service User Guide*.
## Prerequisite Tasks
To set up and run this example, you must first complete these tasks:
+ Install Node.js. For more information about installing Node.js, see the [Node.js website](https://nodejs.org).
+ Create a shared configurations file with your user credentials. For more information about providing a shared credentials file, see [Loading Credentials in Node.js from the Shared Credentials File](loading-node-credentials-shared.md).
## Configuring the SDK
Configure the SDK for JavaScript by creating a global configuration object then setting the Region for your code. In this example, the Region is set to `us-west-2`.
```
// Load the SDK for JavaScript
var AWS = require('aws-sdk');
// Set the Region
AWS.config.update({region: 'us-west-2'});
```
## Retrieving the Current Bucket Policy
Create a Node.js module with the file name `s3_getbucketpolicy.js`. The module takes a single command-line argument that specifies the bucket whose policy you want. Make sure to configure the SDK as previously shown.
Create an `AWS.S3` service object. The only parameter you need to pass is the name of the selected bucket when calling the `getBucketPolicy` method. If the bucket currently has a policy, that policy is returned by Amazon S3 in the `data` parameter passed to the callback function.
If the selected bucket has no policy, that information is returned to the callback function in the `error` parameter.
```
// Load the AWS SDK for Node.js
var AWS = require("aws-sdk");
// Set the region
AWS.config.update({ region: "REGION" });
// Create S3 service object
s3 = new AWS.S3({ apiVersion: "2006-03-01" });
var bucketParams = { Bucket: process.argv[2] };
// call S3 to retrieve policy for selected bucket
s3.getBucketPolicy(bucketParams, function (err, data) {
if (err) {
console.log("Error", err);
} else if (data) {
console.log("Success", data.Policy);
}
});
```
To run the example, type the following at the command line.
```
node s3_getbucketpolicy.js BUCKET_NAME
```
This sample code can be found [here on GitHub](https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/javascript/example_code/s3/s3_getbucketpolicy.js).
## Setting a Simple Bucket Policy
Create a Node.js module with the file name `s3_setbucketpolicy.js`. The module takes a single command-line argument that specifies the bucket whose policy you want to apply. Configure the SDK as previously shown.
Create an `AWS.S3` service object. Bucket policies are specified in JSON. First, create a JSON object that contains all of the values to specify the policy except for the `Resource` value that identifies the bucket.
Format the `Resource` string required by the policy, incorporating the name of the selected bucket. Insert that string into the JSON object. Prepare the parameters for the `putBucketPolicy` method, including the name of the bucket and the JSON policy converted to a string value.
```
// Load the AWS SDK for Node.js
var AWS = require("aws-sdk");
// Set the region
AWS.config.update({ region: "REGION" });
// Create S3 service object
s3 = new AWS.S3({ apiVersion: "2006-03-01" });
var readOnlyAnonUserPolicy = {
Version: "2012-10-17",
Statement: [
{
Sid: "AddPerm",
Effect: "Allow",
Principal: "*",
Action: ["s3:GetObject"],
Resource: [""],
},
],
};
// create selected bucket resource string for bucket policy
var bucketResource = "arn:aws:s3:::" + process.argv[2] + "/*";
readOnlyAnonUserPolicy.Statement[0].Resource[0] = bucketResource;
// convert policy JSON into string and assign into params
var bucketPolicyParams = {
Bucket: process.argv[2],
Policy: JSON.stringify(readOnlyAnonUserPolicy),
};
// set the new policy on the selected bucket
s3.putBucketPolicy(bucketPolicyParams, function (err, data) {
if (err) {
// display error message
console.log("Error", err);
} else {
console.log("Success", data);
}
});
```
To run the example, type the following at the command line.
```
node s3_setbucketpolicy.js BUCKET_NAME
```
This sample code can be found [here on GitHub](https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/javascript/example_code/s3/s3_setbucketpolicy.js).
## Deleting a Bucket Policy
Create a Node.js module with the file name `s3_deletebucketpolicy.js`. The module takes a single command-line argument that specifies the bucket whose policy you want to delete. Configure the SDK as previously shown.
Create an `AWS.S3` service object. The only parameter you need to pass when calling the `deleteBucketPolicy` method is the name of the selected bucket.
```
// Load the AWS SDK for Node.js
var AWS = require("aws-sdk");
// Set the region
AWS.config.update({ region: "REGION" });
// Create S3 service object
s3 = new AWS.S3({ apiVersion: "2006-03-01" });
var bucketParams = { Bucket: process.argv[2] };
// call S3 to delete policy for selected bucket
s3.deleteBucketPolicy(bucketParams, function (err, data) {
if (err) {
console.log("Error", err);
} else if (data) {
console.log("Success", data);
}
});
```
To run the example, type the following at the command line.
```
node s3_deletebucketpolicy.js BUCKET_NAME
```
This sample code can be found [here on GitHub](https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/javascript/example_code/s3/s3_deletebucketpolicy.js).